Opening a ttyport when getty is running

[Sean Sheridan Coleman X5672]

I want to first thank Guy Harris for all of his help he has given me
concerning these tty devices.  I need just a little bit more info (I hope)
to figure all of this out.

The manual states that open will block when opening a device that is a
communication device with no carrier. I confirmed that this works. It also
states that when O_NDELAY is set, the open will not block. 

I also confirmed this. QUESTION: Is the open supposed to succeed?  My open
did with no carrier and O_NDELAY.

Now for the confusion. With login (ie getty engaged) turned on in
/etc/ttytab, the open will block with O_NDELAY set. Reading through the
man pages for the zs devices, I got the idea it is supposed to, but I want
some confirmation because the man pages are not clear about this point. If
it is supposed to hang, has getty done something to make this happen?

Thanks

Sean Coleman
coleman at bldrdoc.gov